THE ADJUSTMENT OF A FIRST-ORDER LEVELLING NETWORK

Abstract

In the E.S.R. January and April numbers of 1955, Vol. xiii, Nos. 95 and 96, Mr. Hsuan-Loh Su described the “Adjustment of a Level Net by Successive Approximations and by Electrical Analogy”. It does not seem to be as generally known as it should be that the rigid least square solution can be greatly simplified by utilizing the electrical analogy and solving by Kirchhoff's method. The method as detailed below has been in use for over 40 years.     

Social media insights on public perception and sentiment during and after disasters: The European floods in 2021 as a case study

Detecting and collecting public opinion via social media can provide near real-time information to decision-makers, which plays a vital role in urban disaster management and sustainable development. However, there has been little work focusing on identifying the perception and the sentiment polarity expressed by users during and after disasters, particularly regional flood events. In this article, we comprehensively analyze tweets data related to the “European floods in 2021” over time, topic, and sentiment, forming a complete workflow from data processing, topic modeling, sentiment analysis, and topic and sentiment prediction. The aim is to address the following research questions: (1) What are the public perception and main concerns during and after floods? (2) How does the public sentiment change during and after floods? Results indicate that there is a significant correlation between a flood's trend and the heat of corresponding tweets. The three topics that receive the most public concern are: (1) climate change and global warming; (2) praying for the victims: and (3) disaster situations and information. Negative sentiments are predominant during the floods and will continue for some time. We tested five different classifiers, of which TextCNN-attention turned out to deliver the best predictions in topic and sentiment prediction, and performed well for sparse flood tweets, it can be used to predict the topic and sentiment polarity of a single tweet in real-time during the flood events. Our findings can help disaster agencies to better understand the dynamics of social networks and develop stronger situational awareness towards a disaster, which can contribute to scientifically justified decision-making in urban risk management and also meet the challenges associated with the global sustainable development goal 11 (SDGs) on Sustainable Cities and Communities.     

A FIFTY-YEARS RETROSPECT

Abstract

The Ordnance Survey after the War.—I might class the four years after the War, during which I remained at the head of the Ordnance Survey, as interesting but troublesome. As is well known, an entirely unreasonable impression was spread about that, now that the War was over, there would be a period of great prosperity, and that we should all live like fighting cocks. Well, things did not work out like that. There was a Select Committee on National Expenditure (1918), and this Committee recommended a lengthening of the period of revision of the large-scale maps of the United Kingdom and a consequent, ultimate, reduction of establishment by 500 men. The Treasury later on insisted on a reduction by 600, including Ireland.     

A SIMPLE PROPOSITION lN,TRIGONOMETRICAL SURVEY AND ITS USES

Abstract

1. The proposition which expresses in terms of the three sides the rate of change of the angle at the vertex of a triangle whose base is stationary and whose vertex is given a small displacement is an important one in plane survey. It must have beeJ1.known to some surveyors for a century or more but there is no doubt that even to-day it is not widely known. This, too, in spite of its extreme simplicity, which makes it, once known, impossible to forget. It's discoverer is unknown to the writer, who was somewhat intrigued to discover it for himself about 25 years ago in the course of field operations of the kind described in § V hereafter. The probability is that many people have discovered it independently.     

SURVEYING INSTRUCTION AT THE UNIVERSITY

Abstract

The title and content of Mr. Ray's contribution to the July number of the E.S.R. entitled “Surveying Instruction at the University” is in the present writer's opinion, somewhat misleading. Obviously he is only referring to the teaching of surveying to civil engineering undergraduates and to students of such other branches of engineering as may be catered for, and does not mention the quite extensive surveying courses associated with the degrees in Geography and Mining at certain Universities. The gist of the article is confusing in that the author concludes by stating that he is “making an honest attempt to assess the merits of the surveying instruction given in the Universities of this country”, which is an admittedly worthy quest but scarcely compatible with some earlier statements such as “the long overdue overhaul of our University courses”, a statement which seems a little premature for one who is still in the stage of “honestly assessing” what is going on.     

THE SURVEYOR'S LEVEL YESTERDAY AND TO-DAY

Abstract

The last twenty-five years have been remarkable for the progress made in the application of science to instrument design and manufacture. Certain instruments such as the Surveyor's Level appeared twenty-five years ago to have almost reached finality of design; but during the intervening period the improvements made have been of so radical a nature that the progress made has been greater than during any corresponding period. In short, the modern level is a more efficient instrument than its prototype and in spite of reductions in size and weight is, capable of yielding more accurate results with a less expenditure of time and energy. In order to appreciate fully how radical these changes have been, a direct comparison may be made between a first-class level as made twenty-five years ago and a similar instrument as made to-day. Twenty-five years ago it was not possible to obtain a level that could be relied upon to remain in adjustment; one that could be quickly checked and easily corrected offered distinct advantages. The Reversible Level was designed with this end in view; and it is proposed to select such an instrument having an objective aperture of 1·65 inches and to compare it with a modern instrument of the same aperture. The focal length of the telescope of the Reversible Level was 16 inches, and the weight of the instrument with its box was 21½ lbs. (Plate VIII, fig. 1). Many surveyors with long experience of this type still speak highly of its reliability and accuracy; it certainly compared very favourably with other instruments of its period.     

RECONNAISSANCE MAPPING FROM TRIMETROGON AIR PHOTOGRAPHS IN THE ANGLO-EGYPTIAN SUDAN

Abstract

Trimetrogon air surveys have been used extensively in the United States and Canada but seem to have had less favour on this side of the Atlantic in spite of the fact that large areas over here were photographed in this way during the last war. The Sudan is a very large country, but not a rich one; and up to the present it has not been able to undertake its own aerial photography. The gift of a very large number of American trimetrogon photographs covering half the country was therefore very welcome, and it seemed worth our while to see what could be done with them in spite of the known disadvantages of this type of photography for anything but small scale mapping. The methods of planimetric mapping from these photographs developed in the United States were expressly designed to be as simple as possible and to be capable of division into a number of easy tasks which could be performed by any educated person after a short course of training. Nevertheless we felt that they could be simplified a great deal more if the problem was approached from a different angle, particularly in view of the very high standard of flying which was apparent in the photographs covering the Sudan.     

SIR DAVID GILL AND THE GEODETIC SURVEY OF SOUTH AFRICA AND THE ARC OF THE 30TH MERIDIAN

Abstract

In the memoir of the late Capt. G. T. McCaw which appeared in the January number of this Review (vii, 47,2), reference was made to the part which the late Sir David Gill played in the origin of the work on the survey of the Arc of the 30th Meridian in Africa. This year is the centenary of Gill's birth, as he was born in June 1843, and it is therefore timely to give some account of his work during his long term of office as Her Majesty's Astronomer at the Cape which resulted inthe inception and completion of the Geodetic Survey of South Africa and the survey of the Arc to the southern shores of Lake Tanganyika. He died on 24th January 1914.     

雷达技术支持下的福州市地铁沿线形变监测

近年来,由于地铁等地下工程大规模的建设产生了严重的地表沉降,从而诱发许多地质灾害,严重阻碍了中国城市化进程。因此,采用高精度雷达监测技术,对城市地质灾害监测及风险评估具有重要意义。本文利用SBAS-InSAR技术,基于24景X波段TerraSAR数据和32景C波段Sentinel-1数据,时间跨度分别为2013年7月至2015年8月、2015年7月至2018年2月,对地铁建设完成后的福州市区地表沉降进行长时间系列形变监测。监测结果表明,研究区域内的最大沉降速率为-12 mm/a,在整个观测周期内发现了8个沉降漏斗。并对这些区域进行进一步的时间序列分析,其中有3个区域呈现出地质灾害初期的特征,并且地表沉降存在进一步加剧的可能。     

Harveys and Walking Maps

Abstract

Geographical information is connected to everyday life in many ways. Web cartography has made geospatial data more available to the public. In the next few years, the average age of the population will be over 51 years, with more than 15% of the population over the age of 65 years. The fact that the senior population is increasing suggests that online mapping and map viewer design should be aware of the senior population’s visual restrictions, as well as restrictions of other potential map users, including colour-vision-impaired users. This paper describes the senior population’s visual restrictions that can be compared with colour-vision-impaired users and provides guidelines with regard to online mapping and map viewer design for this growing segment of the elderly population.     

NOTE ON LEVELLING UP THE PLATE

Abstract

1. The explanation of this fundamental operation in setting up surveying instruments, as well as of the theory of the level on which it is based, is, in my opinion, not sufficiently explained in text-books. I came across the problem while lecturing on the theory of surveying instruments. Below is an extract of the notes I made on the subject, which may have a didactical interest.     

THE COMPUTER—A COG IN THE SURVEY MACHINE

Abstract

1. Lest any reader should be put off by assuming from the title of this article that it would contain a mass of technical matter, it may be stated at the outset that no computations whatever are involved. In fact it is a collection of very ordinary observations pertaining to the efficient functioning of the computing section of a Survey Department. In the opinion of the writer nothing clarifies one's ideas more than sitting down at a table and putting them actually on paper. Things that might otherwise have been overlooked or forgotten are brought to light, and can then be given their proper place in the whole mosaic. There is probably nothing original in this article, yet it is hoped that a comprehensive survey may be of assistance to other computers, as the making of it certainly has been to the writer. It has been written from the point of vievvof a computing section, rather than that of an individual computer. Each individual computer is a cog in the computing machine, whose duties are more those of routine calculation by methods approved by his superior.     

THE QUEST FOR CAMERON'S PLATEAU

Abstract

A Newcomer to Malaya visiting Cameron Highlands for the first time may probably wonder, after his car has made its tortuous ascent into the mountains, how this area became Malaya's main hill station and why it received its name. He may not know that years before the Highlands came under serious consideration and after it was obvious the development of Fraser's Hill could only be limited, Gunong Tahan, the highest mountain in the peninsula (7,186 feet) on the borders of Kelantan and Pahang, was for a long time considered as Malaya's only hope of a hill station likely to rival those of India and Ceylon. In fact, a topographical survey made by the Federated Malay States Survey Department just before and during the 1914–18 war revealed the presence there of an extensive plateau at a height of about 5,400 feet, It seemed so promising that in 1912 the Governor, Sir Arthur Young, made the ascent on foot to inspect it. However, before coming to a decision Government considered it advisable to test the climatic conditions there, and accordingly a party of observers was recruited from England for the purpose. They spent a year on Gunong Tahan between 1921 and 1922 and subsequently made a report on their observations. Opinion then became unfavourable, partly because the plateau is but imperfectly furnished with soil, partly because it is somewhat inaccessible from most of the inhabited areas of the peninsula, and partly because during too many days of the year it is liable to become enshrouded in heavy mists. The idea of immediately developing Gunong Tahang was therefore abandoned. Those who thought they saw in this mountain another Newara-Eliya or Ootacamund were naturally disappointed and soon cast around for another site to accommodate the hill station of their dreams. In this quest someone remembered or alighted upon in the archives of the Perak Public Works Department a report by an explorer named William Cameron on his journey overland about 1884 from Kinta to the mouth of the Pahang River. The late Sir Frank Swettenham, in his last book, “ Footprints in Malaya “, published by Hutchinson & Co., Ltd., London, in 1942, throws some light on Cameron and his activities about this time. He says, “ Amongst the strangers from Ceylon and India, from Shanghai, Hong-Kong, Australia and elsewhere, who strayed into Selangor was Mr. William Cameron, brother of the editor of the Straits Times, a highly respected resident of Singapore. Mr. William Cameron came to Selangor shortly after I became British Resident there, and he asked to be allowed to do something which would help in the development of the country. His culture and his quiet manner appealed to me, and I asked him what he proposed to do. He explained that he had some knowledge of minerals and geology, and he suggested that he should be given a roving commission to go, with a party of wild people whom he would collect, and explore the depths of the jungle and report the result of his search …. I engaged Mr. Cameron to do what he suggested. He made all his own arrangements, managed somehow to collect a party of aborigines, and disappeared into the jungle for weeks at a time. When he returned from these expeditions he used to come to the Residency, stay a few days, make his report and start off again. After one prolonged absence, when I became anxious about his safety, he returned very ill and had to be carried the last stage of his journey. He then reported the discovery of the high table-land on the borders of Perak and Pahang, now known as Cameron Highlands. I do not know what had upset him, unless it was the hardships he went through in those many weeks of travel up and down the jungle-covered mountains of the main range, but while he stayed with me he was subject to strange delusions, walked about the house at 3 a.m., carrying an iron bar, and two or three times in a night I had to put him back in his bed. Finally, one morning, he produced a revolver and shot at his Chinese servant, and when I went to his room and told him I had removed all his firearms because of that incident, he merely remarked: ‘Yes, but I didn't ·hit him.’ Eventually it was necessary to send him to the Singapore Hospital’ for proper care, and there he died.”     

PERSONALIA

Abstract

The death occurred suddenly on 2nd February, 1935, of Mr. WILLIAM ERNEST BARRON,of Fort Jameson, Northern Rhodesia. Mr. Barron, who was 55 years of age, held the Certificate of Land and Mine Surveyor of the School of Mines, University of Otago, New Zealand, and the Mine Surveyor's certificate of competency, Transvaal, and in 1913 was licensed as a surveyor in Northern Nigeria. In 1921 he was licensed as a surveyor for private practice in Northern Rhodesia. He was for over four years Chief Surveyor to the Van Ryn Gold Mines Estate, Ltd., and for two years to the Bantjes Consolidated Mines, Ltd., and for some time to Modderfontein East, Ltd. He was first employed in Northern Rhodesia as Mine Captain in charge of survey work at Broken Hill Mine, and from 1923 to 1928 was engaged by the Rhodesia Broken Hill Development Co., Ltd., in the survey and setting out of all work in connexion with that Company's Hydro-Electric Power Scheme at Mulungushi. Upon the completion of this work, in which Mr. Barron showed the greatest skill and accuracy under difficult conditions, he was engaged by the North Charterland Exploration Company as surveyor, and at the time of his death he was carrying out the survey of that Company's Land Concession, an area of 10,000 square miles on the south-eastern border of Northern Rhodesia. By his death the survey profession has lost an able and keen personality, and he will be greatly missed by the many friends he made in this country. He leaves a widow and son to mourn his loss.     

三维地质模型数据Geo3DML向3DPDF格式转换

针对目前三维地质模型数据格式繁多,交换困难的问题,该文介绍了中国地质调查局颁布的三维地质模型数据交换格式标准(Geo3DML)及其向3DPDF文件转换的必要性和实现的技术途径。首先简单介绍了Geo3DML的背景、制定过程、标准概况与试用情况;然后介绍了3DPDF的背景与用途;接着介绍了3DPDF所依赖的U3D格式的背景;最后介绍了用C++编程实现Geo3DML向3DPDF转换的技术途径和一些关键技术以及对数据输出质量控制的选项设置方法。转换结果能够较好地表达三维地质模型几何特征和属性特征。     

The role of the Ordnance Survey of Great Britain

Abstract

This paper is concerned with the future of the British national mapping agency in a society which is markedly different from that in which the Ordnance Survey Review Committee of 1979 worked. The objective is to ascertain which topographic information is needed, who should provide it, on what terms and through which mechanisms. Prior to making an attempt to answer these questions, the essential characteristics of Ordnance Survey (OS) are summarised as deduced from available documentary evidence; the changing attitudes to information as a commodity, the growing competition in British mapping and the government's stringent requirements from the Survey are also outlined as just three of the many complexities which affect OS. Building upon Smith's classic 1979 paper and subsequent experience, the rationale for government involvement in mapping is examined. It is concluded that the Survey has a continuing vital role though there are a number of steps which the OS should take in order to adapt to changing circumstances.     

John Keates and Recreation Mapping: Personal Recollections

Abstract

John Keates is very well known for his numerous scholarly contributions to cartography as an academic discipline and science. However, throughout his career, he was also very actively involved in the design and production of maps. Mostly these were specialized thematic maps produced as the result of scientific research in the field sciences, especially in geology, glaciology and vegetation studies. However, during the 1970s he was much involved in the design and production of a considerable number of maps for recreation purposes, including maps for orienteering. Many of these maps were regarded at that time as being extremely innovative in terms of their cartographic design and layout. The article outlines the development of what became known as the 'Glasgow' style of map design John Keates' involvement with recreation maps in the 1970s.